The list of banks advising on a global exchange mega merger has just got even bigger with Nasdaq OMX and InterContinental finally submitting their joint bid for NYSE Euronext. Financial News has calculated a total of 16 advisers that are now advising on at least one large M&A exchange deal. However, there is one bank notable by its absence: Citigroup.

Citgroup is the only firm in the top 10 advisers in global M&A last year that has yet to be named as an adviser. This begs the question: has it been left behind - or is the US firm been advising another exchange merger behind the scenes? Citigroup declined to comment.